The present invention relates to a thin film transistor using an oxide semiconductor for a channel layer and a display device using the same.
A display device includes a TFT substrate on which pixels having a pixel electrode, a thin film transistor (TFT), and the like are formed in a matrix configuration and the TFT substrate is disposed opposite to a counter substrate on which a color filter or the like is formed at a location corresponding to the pixel electrode of the TFT substrate. In a liquid crystal display device, liquid crystal is sandwiched between a TFT substrate and a counter substrate. The light transmittance of liquid crystal molecules is controlled for individual pixels, and images are formed.
Presently, with a rapid spread of Smartphones (registered trademark) and tablet devices, a liquid crystal display (LCD) adapted to these devices is strongly demanded to have high definition, low power consumption, and a decrease in cost. In order to meet these demands, the development of an oxide TFT for an LCD TFT substrate is actively conducted, which uses TAOS (Transparent Amorphous Oxide semiconductors) having a mobility greater than the mobility of amorphous Si (a-Si), more specifically an IGZO (Indium Gallium Zinc Oxide) film for a channel layer (see Japanese Patent Application Laid-Open No. 2010-67849, for example). Moreover, micro-processing techniques for interconnections are disclosed in Japanese Patent Application Laid-Open No. 2013-4606, for example.